Roofing composite including dessicant and method of thermal energy management of a roof by reversible sorption and desorption of moisture

Abstract

A roof system is secured to a roof deck on a building. The roof system has a thermal energy absorbing product including a desiccant located between the roof deck and a roof barrier. The desiccant reversibly absorbs moisture, and in response thereto, heat is released and absorbed by the desiccant to effect a thermal management of the roof system.

What is claimed is: 
     
       1. A roof system for a building having an attic in an interior of the building, the roof system comprising:
 a roof deck on an exterior of the building above the attic; 
 a roof product secured to the roof deck, opposite the attic; and 
 a thermal energy absorbing product (TEAP) that is a stand-alone product separate from but located between the roof deck and the roof product, the TEAP comprises a desiccant that reversibly absorbs moisture, and in response thereto heat is released and absorbed, respectively, by the desiccant to effect a thermal management of the roof system, 
 the TEAP comprises a rigid sheet or a rigid panel, and the roof product is an asphaltic roof shingle; and a ventilation channel inside an interior of the TEAP adjacent the desiccant, whereby air having a humidity flowing through the ventilation channel transports moisture to and from the desiccant, and the heat released and absorbed by the desiccant effects thermal management of the roof system. 
 
     
     
       2. A roof system according to  claim 1 , wherein the desiccant comprises a powder or sheet form, and the desiccant comprises about 5 wt % to about 50 wt % of the TEAP. 
     
     
       3. A roof system according to  claim 1 , wherein the TEAP comprises a non-woven mat, glass mat, woven mat, scrim, felt, Kraft paper, honeycomb board, channeled panel, industrial fabric, recycled mat, porous ceramic board, cementitious board, wood composite, plastic wood, inorganic bonded composite, gypsum board, or any combination thereof, and the desiccant comprises media without an adhesive. 
     
     
       4. A roof system according to  claim 1 , further comprising a skin layer adjacent the desiccant, and the skin layer has a moisture permeability of greater than 2 perm. 
     
     
       5. A roof system according to  claim 1 , wherein the desiccant comprises clay, nano-clay, montmorillonite clay, synthetic zeolite, surface modified carbon, carbon molecular sieve, activated carbon, calcium oxide, calcium sulfate, salt, inorganic salt, silica gel, activated alumina, polymeric desiccant material, cellulose material, metal silicate, or any combination thereof. 
     
     
       6. A roof system according to  claim 1 , wherein the desiccant is a powder or in an encapsulated form with a size in a range of about U.S. mesh #10 to about U.S. mesh #325. 
     
     
       7. A roof system according to  claim 1 , wherein the TEAP is directly nailable for roofing shingles on top thereof without affecting an overall thickness and functionality of the TEAP, and the desiccant has a thickness in a range of about 0.25 inches to about 1 inch. 
     
     
       8. A roof system according to  claim 1 , further comprising at least one of a fire retardant, an anti-microbial addition, a UV stabilizer and a UV protection layer. 
     
     
       9. A roof system according to  claim 8 , wherein the desiccant and fire retardant form a unitary structure. 
     
     
       10. A roof system according to  claim 9 , wherein the unitary structure comprises less than about 25% of the fire retardant. 
     
     
       11. A roof system according to  claim 8 , wherein the fire retardant comprises at least one of expandable clay, expandable carbon black, expandable graphite, intumescent silicates, hydrated metal silicates, bromated compounds, halocarbons, aluminum hydroxide, magnesium hydroxide, hydromagnesite, antimony trioxide, various hydrates, red phosphorus, boron compounds and phosphonium salts. 
     
     
       12. A roof system according to  claim 8 , further comprising a skin layer having an uppermost layer and a lowermost layer, between which are located the desiccant. 
     
     
       13. A roof system according to  claim 1 , wherein the TEAP has an effective heat of absorption to regulate at least 5% of solar energy incident thereon. 
     
     
       14. A roof system according to  claim 1 , wherein the TEAP is flexible at a temperature of about 0° C., and remains structurally sound for a roof walkable surface at a roof surface temperature of about 70° C. 
     
     
       15. A roof system according to  claim 1 , wherein the desiccant has a heat of absorption of greater than about 20 kJ/mol-H 2 O to store solar heat during a heating cycle, and a thermal emittance of greater than about 0.70 that re-radiates stored heat during a cooling cycle. 
     
     
       16. A roof system according to  claim 1 , wherein the desiccant has a heat of absorption of less than about 70 kJ/mol-H 2 O to store solar heat during a heating cycle, and a heat absorbing range of about 10° C. to about 50° C. 
     
     
       17. A roof system according to  claim 1 , wherein the TEAP has a plurality of cells configured to be penetrated by roofing fasteners, and the cells are void of the desiccant. 
     
     
       18. A roof system according to  claim 1 , wherein the TEAP further comprises an upper radiant barrier and a lower moisture barrier, and components of the TEAP comprise the only materials located between the roof deck and the roof product. 
     
     
       19. A roof system according to  claim 1 , wherein the TEAP has a thickness of about 0.75 inches to about 2.5 inches. 
     
     
       20. A roof system according to  claim 1 , wherein the TEAP has a weight in a range of about 1 pound per square foot to about 10 pounds per square foot.